Electrically insulated chuck for hand-held drills

ABSTRACT

A chuck including a rotatable metal body carrying jaws that are adjustable for holding a work bit. The body has a metal insert press fitted into a cavity for drivably coupling the body to the spindle of a hand-held drill. A coating of nylon plastics over the outer surface of the insert electrically insulates the body of the chuck from the insert and, as a consequence, from the spindle. In a further embodiment, the spindle itself is coated with the nylon plastics material and is press fitted into the body of the chuck.

United States Patent [191 McCarthy Mar. 19, 1974 ELECTRICALLY INSULATEDCHUCK FOR HAND-HELD DRILLS [75] Inventor: Donald J. McCarthy,Wethersfield,

Conn.

[73] Assignee: The Jacobs Manufacturing Company, West Hartford, Conn.

[22] Filed: Feb. 23, 1972 [21] Appl. No.: 228,561

[52] US. Cl 408/240, 408/710, 279/1 Q, 174/138 D [51] Int. Cl B231)31/12 [58] Field of Search 279/1 Q, 60; 408/710, 240; 310/50. 47;174/138 D [56] References Cited UNITED STATES PATENTS Jacyno 279/1 Q3/1966 Gubbins 310/50 X 7/1969 Badcock 310/50 Primary Examiner-GilWeidenfeld Attorney, Agent, or Firm-Stephen J. Rudy ABSTRACT A chuckincluding a rotatable metal body carrying jaws that are adjustable forholding a work bit. The body has a metal insert press fitted into acavity for drivably coupling the body to the spindle of a handhelddrill. A coating of nylon plastics over the outer surface of the insertelectrically insulates the body of the chuck from the insert and, as aconsequence, from the spindle.

in a further embodiment, the spindle itself is coated with the nylonplastics material and is press fitted into the body of the chuck.

2 Claims, 5 Drawing Figures ELECTRICALLY INSULATED CHUCK FOR HAND-HELDDRILLS BACKGROUND OF THE INVENTION This invention is concerned with anelectrically insulated chuck for drills of the hand-held type.

Conventional portable, hand-held drills have a housing containing arotary motor for driving a spindle carrying a chuck. The chuck andspindle as well as the housing are formed of electrically conductivematerial. In operating a conventional hand-held drill. there is apossibility that the chuck. or the work tool carried by the chuck, maystrike a live electrical wire. A consequence of such an accident couldbe the passing of a dangerous current from the chuck through the spindleand housing to the operator.

The objective of this invention is to provide a solution to this problemby insulating in a practical manner the chuck from the spindle so thatan electrical current cannot pass from one to the other.

In accordance with the invention, I have provided a chuck which isattachable to the spindle of a rotary tool by means of an insert memberof the chuck which is electrically insulated from the rest of the chuck.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 illustrates a chuck embodying the invention mounted upon thespindle of a power tool, the chuck is shown broken away in part tobetter disclose its coupled relation to the spindle;

FIG. 2 is a fragmentary detail of the rear portion of the body of thechuck without the insert;

FIG. 3 is a detail of the insulated insert element of the chuck;

FIG. 4 is a right end view of FIG. 3; and

FIG. 5 shows a further embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT In the accompanying drawingillustrating the invention, there is disclosed a conventional power toolof the hand-held type having a motor driven spindle 11 supported in ahousing 12 for driving a chuck 13. Only so much of the power tool 10 isshown as required to provide an adequate understanding of the invention.The metal spindle I1 is rotatably supported in the usual metal bearing(not shown) supported by the metal housing 12. Accordingly, the spindleis capable of conducting an electrical current to the housing, as wellas to other internal metal components of the tool.

The chuck 13 includes a body member 14 having the usual inclined jawtracks 16. Jaws 15 are caused (in conventional manner) to slide in thetracks to and from gripping relation with a work element (not shown)upon actuation of a rotatable sleeve nut 17. The latter has an internalthreaded engagement with the jaws for this purpose. The body ofthechuck, as well as the jaws, and sleeve nut, are formed of metal.Accordingly, an electrical current could be passed from the jaws orsleeve nut to the body of the chuck.

Means is provided for drivingly connecting the body of the chuck withthe spindle and for electrically insulating it from the spindle. Thismeans is defined by an insert 19 fixed to, and made unitary with, thebody of the chuck. The insert is tightly press fitted into a cavity 21extending axially into the rear end of the body of the chuck. The inserthas an axially extending threaded bore 22 in which the threaded end ofthe spindle 11 is engageable.

To ensure a non-failing strong threaded connection with the spindle..theinsert has a metal body 23. The body of the insert is provided with athin surface coating or film 24 of electrically non-conductive plasticsmaterial, such as nylon. The nylon coating effectively insulates thebody 14 of the chuck electrically from the body of the insert and, as aconsequence. from the spindle 11 connected to the insert.

The nylon coating covers over the entire outer surface area of theinsert with the exception of its rear face 25 so that the entire wallarea of the cavity 21 in the chuck body is separated from the metal bodyof the insert by the nylon coating.

While it is not needed to coat the rear face 25 of the insert with theinsulating material, nevertheless, the entire outside surface of theinsert may be coated.

It has been found that a nylon coating from 0.005 to 0.015 in thicknessprovides satisfactory insulating characteristics. The coating is adheredor bonded to the insert. This may be done in any suitable manner. Forexample, it may be done by initially heating the insert to a propertemperature and then spraying it with the plastics material so as tocause the latter to adhere in bonded relation to the insert.

The insert is shown as projecting axially beyond the rear face of thebody of the chuck, as at 26. This projecting end ensures against contactbeing made between any part of the spindle and the body of the chuck.The projecting end of the insert serves as an abutment or spacer againstwhich a collar 27 on the spindle may be brought without coming intocontact with the adjacent end face of the body 14 of the chuck. It alsoserves to space the nose of the tool's housing 12 a desirable distancefrom the chuck so as to prevent spark jumping.

It is also to be noted that the bore 22 in the insert does not openthrough the front end of the insert so that the insulated forward end ofthe insert blocks communication of the bore with the bottom of thecavity. This is of advantage in that the spindle is prevented from beingexposed through the insert to the bottom of the cavity and any foreignmetal particles that might have attained access to the cavity areprevented from contacting the spindle.

While the coating of insulating material is shown as applied to theinsert, it is understandable that it could be applied to cover theinternal wall of the cavity 21 as well as the rear end face 28 of thebody of the chuck.

In the FIG. 5 embodiment, the coating 29 of insulating material is shownas applied to the spindle 31 of the tool; and the spindle with thecoating thereon is rigidly press fitted in an axial bore 32 of the body33 of the chuck so that the body and spindle rotate as a unit.

I claim:

1. In a power tool including a housing supporting an electricallypowered motor driven metal spindle, a tool chuck having a metal bodyformed with an axially extending cavity in its rear end, and couplingmeans for coupling the body of the chuck to the spindle, the couplingmeans comprising a metal bushing having a film of electrical insulatingplastics bonded to its surface insulating the bushing from the wall ofthe cavity and formed with an axial bore ih which the spindle isprojects axially rearwardly from the body of the chuck into abutmentwith a metal collar on the spindle whereby an electrically insulatingair gap is provided spacing the collar of the spindle from the rearmostpart of the metal body of the chuck.

1. In a power tool including a housing supporting an electricallypowered motor driven metal spindle, a tool chuck having a metal bodyformed with an axially extending cavity in its rear end, and couplingmeans for coupling the body of the chuck to the spindle, the couplingmeans comprising a metal bushing having a film of electrical insulatingplastics bonded to its surface insulating the bushing from the wall ofthe cavity and formed with an axial bore in which the spindle isthreadedly received, the bore extending only partway into the bushing,and the surface of said insulated metal bushing being of a predeterminedsize and of a shape complementary to the chuck cavity to have beenreceived therein by a press fit.
 2. In a power tool as in claim 1,wherein the bushing projects axially rearwardly from the body of thechuck into abutment with a metal collar on the spindle whereby anelectrically insUlating air gap is provided spacing the collar of thespindle from the rearmost part of the metal body of the chuck.